Sanford, N.C. — Six people were injured Thursday morning when a pickup truck slammed into the back of a school bus picking up a student on N.C. Highway 42 in Sanford, Lee County Schools officials said.

Emergency crews responding to the wreck around 7:40 a.m. found four children injured on the bus and two people, including another child, injured in the pickup truck.

The truck's driver, Brian Warren, 17, a student at Southern Lee High School, was airlifted to UNC Hospitals in Chapel Hill, State Trooper Greg Ingram said. Warren's 7-year-old brother, River Warren, a student at J.R. Ingram Elementary School, was also transported by ambulance to UNC Hospitals.

The extent of their injuries was not immediately known. Ingram, however, said it did not initially appear that they were life-threatening.

Four children on the school bus were taken to a Central Carolina Hospital in Sanford with minor injuries, school district officials said.

Authorities said the school bus, which was carrying 31 students and two adults, was on its way to J.R. Ingram Elementary and was stopped with its stop arm out and lights flashing at the time of the wreck.

"The impact was incredible," said Carrie Howard, a bus monitor who was on board at the time of the crash. "Honestly, it sounded like a bomb going off."

Howard said she ran to the back of the bus to check on the children, and that's when she noticed the truck.

"It was just demolished," she said. "I could not believe it, and my first thought was, 'How could anybody survive that?'"

Howard said she also recognized both of the Warren boys.

"It just broke my heart to see him laying there with a neck brace and struggling in pain," she said of one of the boys. "I just wanted to get him out."

The wreck remains under investigation, and authorities said a determination of charges would be decided after everyone involved has been interviewed.

Guidance counselors from other Lee County schools were sent to the school to counsel students.